Sensors usually only require a very small current, not enough to worry about.
There are exceptions, like gas sensors which have a heating element inside them and so need quite a large current. But your photo sensors will require only a tiny current.
The Arduino itself will probably need 20~30mA.
Where did you read this? I think you misunderstood. The L298 will draw very little current for itself, a few mA. But it is powering the motors, and they will probably require hundreds of milliamps for each motor.